It has conventionally been known that making metal particles small to be nano-sized presents functions that are not observed when they are in a bulk state, and localized plasmon resonance is in particular expected for application. Plasmon is a compressional wave of free electrons that arises by collective oscillation of the free electrons in a metallic nanostructure.
In recent years, a field of art handling the plasmon is referred to as plasmonics and attracts large attention, and has also been actively studied and such study includes exploiting phenomena of localized plasmon resonance of a metal nanoparticle to be intended for improvements of light emitting devices in luminous efficiency and improvements of photoelectric conversion devices (solar cell devices and the like) in conversion efficiency.
Japanese Patent Laying-Open Nos. 2007-139540 (PTD 1) and 08-271431 (PTD 2) and WO2005/033335 (PTD 3), for example, disclose techniques exploiting localized plasmon resonance for enhanced fluorescence. Furthermore, T. Fukuura and M. Kawasaki, “Long Range Enhancement of Molecular Fluorescence by Closely Packed Submicro-scale Ag Islands”, e-Journal of Surface Science and Nanotechnology, 2009, 7, 653 (NPD 1) indicates a study on localized plasmon resonance of silver nanoparticles.